In order to perform a successful epidermal growth factor receptor (EGFR) mutation test, a sufficient quantity of tumour cells is required to ensure that an adequate amount of tumour DNA is extracted for analysis.1–3 The two main sample types used for evaluating the EGFR mutation status are tumour biopsy and circulating tumour DNA (ctDNA) samples obtained from blood (plasma).
At diagnosis of advanced non-small cell lung cancer (NSCLC), a tumour biopsy is the preferred sample type for evaluating EGFR mutation status. At disease progression following treatment with an EGFR-tyrosine kinase inhibitor (TKI), a tumour biopsy is recommended.10
It is important that guidelines are followed when obtaining, fixing and handling tumour biopsy samples, and when performing an EGFR mutation test:1,11,12
In many patients with advanced NSCLC, ctDNA is present in the blood.13 At primary diagnosis of advanced NSCLC, when a tumour biopsy is not available, ctDNA from blood (plasma) samples provides an alternative for evaluating EGFR mutation status.
Based on the results from the Phase IV IFUM study, gefitinib was the first EGFR-TKI to allow the use of ctDNA (obtained from a blood sample) to assess for EGFR mutation status at diagnosis in those patients where a tumour sample was not available (EU label only).3,14
Following disease progression on an approved EGFR-TKI, it can be more challenging to obtain a tumour biopsy than at primary diagnosis. A ctDNA sample obtained from blood (plasma) offers a less invasive and potentially quicker alternative for EGFR mutation testing.
The Phase II AURA2 study assessed the activity and safety of the 3rd generation EGFR-TKI, osimertinib, in patients who had progressed following treatment with an approved EGFR-TKI. This study supported the need for biopsy at the time of disease progression.15
For ctDNA testing, to avoid blood coagulation and cell lysis, EDTA tubes may be used if the blood sample is to be processed quickly, however, stabilisation collection tubes provide an alternative when this is not possible (e.g. Streck Cell-Free DNA blood collection tubes, Roche Cell-Free DNA collection tubes, PAXgene Blood ccf-DNA Tubes).16-18
Please note: heparin collection tubes must not be used as this can interfere with downstream PCR applications.21